The following relates generally to wireless communication, and more specifically to a listen-before-talk (LBT) interface for logical discontinuous transmission (DTX).
Wireless communications systems are widely deployed to provide various types of communication content such as voice, video, packet data, messaging, broadcast, and so on. These systems may be capable of supporting communication with multiple users by sharing the available system resources (e.g., time, frequency, and power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, and orthogonal frequency division multiple access (OFDMA) systems. A wireless multiple-access communications system may include a number of base stations, each simultaneously supporting communication for multiple communication devices, which may be otherwise known as user equipment (UE).
Wireless wide area networks (WWANs) may be scheduled networks with a base station used as a single control entity to notify each user equipment (UE) of the allocated frequency-time resources (e.g., physical resource block pairs). The UE may be scheduled by a control channel (e.g., Physical Downlink Control Channel (PDCCH) or enhanced Physical Downlink Control Channel (ePDCCH)) to receive downlink (DL) traffic. Further, the UE may receive the DL traffic in a data channel (e.g., Physical Downlink Shared Channel (PDSCH)). In some cases, WWANs may operate in an unlicensed band (e.g., together with a wireless local area network (WLAN)). Compared to a WLAN, a WWAN may enjoy better link performance, medium access control, mobility management, or improved coverage.
Regulatory standards for operating in a shared or unlicensed band (e.g., the 5 GHz band) may include performing a Clear Channel Assessment (CCA) or a listen-before-talk (LBT) mechanism for channel sensing prior to transmission. If the LBT procedure is carried out by the physical (PHY) layer, higher layers (e.g., the media access control (MAC) layer) may be unaware of whether the channel is checked out. That is, without notification of a failure to access a channel, the higher layers may assume that the DL traffic was decoded unsuccessfully by the UE, which may influence link adaptation of the data or control channels. The higher layer scheduling may schedule a retransmission, which may be inefficient as the traffic was not originally transmitted. This may result in missed packets, delays, or reduced throughput.